1. Field of the Invention
The present invention is related to a method of making very low profile fine wire interconnections between a conductive pad on a semiconductor device and a target bonding point on a lead frame or lead of a package. More particularly, the present invention relates to a novel method of forming slack free low profile fine wire interconnections between terminals on an integrated circuit and the lead out pads on a lead frame or package.
2. Description of the Prior Art
Automatic wire bonders are employed to make fine wire interconnections between semiconductor devices and lead out pads. Such automatic wire bonders are shown and described in U.S. Pat. No. 4,266,710 and are provided with microprocessor controls which enable the automatic wire bonder to be programmed to move its capillary bonding tool in a predetermined path at a predetermined velocity. The programmed path is different from the shape of the final fine wire interconnection and involves special method steps and knowledge of the resilience, strength, wire type and size of the fine wire being bonded.
U.S. Pat. No. 4,327,860 shows and describes a preferred method of making standard profile slack free fine wire interconnections. While this prior art method produces repeatable standard profile fine wire interconnections, it was found to be incapable of making low profile or very low profile interconnections of the type required for a use in Thin Small Outline Package (TSOP) applications such as smart cards. Thin packages require that the fine wire interconnections be slack free and have a loop height in the order of 3 to 10 one-thousandth of an inch (mils). While such interconnections can be made using special rotary head wedge bonders or Tape Automatic Bonding (TAB), at the time the present invention was made and tested it was not believed possible to make low profile fine wire lo interconnections for TSOP packages using an automatic gold wire ball wire bonder.
It would be highly desirable to provide a method of making low profile and very low profile fine wire interconnections using highly accurate and reliable automatic gold wire ball bonders.